Five Things to Know About Princess Beatrice

We may not know the royal wedding guest list just yet, but here's one family member whose name is surely in the "definite" category.

Princess Beatrice, 22, is Prince William's first cousin (her father, Prince Andrew, is Prince Charles's brother), and she is fifth in line to the throne in the royal pecking order. Her immediate family is well-known, too: Beatrice's mother is Sarah Ferguson, the Duchess of York, and her younger sister, Eugenie, is another young princess to watch.

What else is there to learn about this royal redhead?

1. She worked hard for that body!Beatrice lost about 20 lbs., thanks to her training for the London Marathon last April, along with all the boxing and squats she did to prepare. She's made headlines for her new svelte frame – certainly a welcome change from the buzz in 2008 when unflattering bikini photos surfaced in the press. "I could have kicked myself for wearing it," she told the Daily Mail of her suit choice.

2. Who's that guy?The princess attended the wedding of Harry Aburey-Fletcher on Jan. 8 (along with Prince William and Kate Middleton) with her long-term boyfriend Dave Clark on her arm. Her beau, the son of millionaire Michael Clark who works for Richard Branson at Virgin, has already got the stamp of approval from Beatrice's mother. The Duchess of York calls Clark 'Mr. Smiley,' "because he smiles and he's happy," she said. "I love Dave. He's cool."

3. Her Royal Highness, the college studentBeatrice – full name: Princess Beatrice Elizabeth Mary of York – and her sister Eugenie are the only granddaughters of the Queen whose names are preceded by the royal style, "Her Royal Highness." Their cousins Lady Louise Windsor and Zara Phillips do not hold this distinction. HRH Princess Beatrice began her history studies at London's Goldsmiths University in 2008 and is expected to graduate this year.

4. She's quite charitableLike her royal relatives, this princess is highly active in charitable works. She has visited children with HIV in Russia and supported the U.K.'s Springboard for Children, which supports school children with learning difficulties. Most notably, it was for her mother's Children in Crisis charity that she ran the London Marathon – and she was the first member of the royal family to complete the race. Beatrice also happened to be the first member of the British royal family to appear in a movie with her small role in 2009's The Young Victoria.

5. She may be one of the next royals to say 'I do'Even with more than three months to go until Will and Kate's big day, there's already chatter about the next royal wedding. Beatrice's romantic New Year's trip with her boyfriend sparked a new round of speculation that the pair could be getting hitched soon after Will and Kate.